Method for manufacturing stator of rotary electric machine including cassette coil

ABSTRACT

A method is for manufacturing a stator of a rotary electric machine. The method includes; forming a stator core; forming each of cassette coils by concentrically winding rectangular wire for the specified number of turns, each of the cassette coils being formed by applying a shift amount with respect to an axis in a winding direction to a wire shape of at least one of the turns before being attached to the teeth; attaching each of the cassette coils to each of teeth while canceling the shift amount; and forming a wire coil of the rotary electric machine by connecting a winding terminal of one of the cassette coils to a winding terminal of another of the cassette coils.

INCORPORATION BY REFERENCE

This is a divisional of U.S. application Ser. No. 15/230,705 filed Aug.8, 2016, which claims priority to Japanese Patent Application No.2015-158382 filed on Aug. 10, 2015, the disclosure of which, includingthe specification, drawings and abstract, is incorporated herein byreference in its entirety.

BACKGROUND 1. Field

The present disclosure relates to a method for manufacturing a stator ofa rotary electric machine and a cassette coil for a rotary electricmachine used therefor.

2. Description of Related Art

As methods for winding a coil that is wound around plural teeth of astator of a rotary electric machine, concentrated winding in whichone-phase wire is wound around one of the teeth and distributed windingin which the one-phase wire is wound across the plural teeth have beenknown.

It is described in Japanese Patent Application Publication No.2015-073386 (JP 2015-073386 A) that, as a stator of a three-phase rotaryelectric machine, a coil piece that is formed by concentrically windingwire formed of rectangular wire is attached to each of plural teeth ofthe stator, and ends of the coil pieces in the same phase are connectedto each other.

The concentrated winding coil can be prepared in advance as the coilpiece, in which the wire is wound, in such a manner as to correspond toeach of the teeth of a stator core. This is called a cassette coil. Inorder to assemble the cassette coil to the stator core, an assemblyclearance in certain width is required. In the related art, in order toprevent the cassette coil from coming off the stator core because ofthis assembly clearance, another member having a claw and the like forfixing the cassette coil to the stator core is used.

SUMMARY

The disclosure provides a method for manufacturing a stator of a rotaryelectric machine capable of fixing a cassette coil to a stator corewithout using a special fixing member and a cassette coil for a rotaryelectric machine used therefor.

A method for manufacturing a stator of a rotary electric machineaccording to one aspect of the present disclosure includes: forming astator core having teeth that are projected from an annular stator yoketo a radially inner side; forming each of cassette coils byconcentrically winding rectangular wire for the specified number ofturns, each of the cassette coils being formed by applying a shiftamount with respect to an axis in a winding direction to a wire shape ofat least one of the turns before being attached to one of teeth;attaching the cassette coils to each of the teeth while canceling theshift amount; and forming a wire coil in the rotary electric machine byconnecting winding terminals of the cassette coils to each other.

According to the method for manufacturing the stator of the rotaryelectric machine having the above configuration, the cassette coil thatis formed by concentrically winding the rectangular wire and formed byapplying the specified shift amount with respect to the axis in thewinding direction to the wire shape of at least one of the turns beforebeing attached to one of the teeth is used. The cassette coil has aproperty of a coil spring and can have appropriate coil springelasticity by using the rectangular wire therefor. By using this coilspring elasticity, the cassette coil can be attached while applying areaction force of the spring elasticity, which is generated bycancellation of the shift amount, to each of the teeth.

A method for manufacturing a stator of a rotary electric machineaccording to another aspect of the present disclosure includes: forminga stator core having teeth that are projected from an annular statoryoke to a radially inner side; forming each of cassette coils byconcentrically winding rectangular wire for the specified number ofturns, each of the cassette coils being formed by applying a shiftamount with respect to an axis in a winding direction to a wire shape ofat least one of the turns before being attached to the stator core;arranging each of insulators on outer circumferential side surfaces ofeach of the teeth, the insulator having a cylindrical shape and heldbetween an inner circumferential side surface of the cassette coil andthe outer circumferential side surface of each of the teeth that opposesthe inner circumferential side surface of the cassette coil, and theinsulator being provided with a step on an outer side surface of saidcylindrical shape that corresponds to an inner circumferential sidesurface of each of the turns of the rectangular wire; bringing the innercircumferential side surface of each of the turns of the rectangularwire into contact with the step of each of the insulators whilecanceling the shift amount, and attaching each of the cassette coils;and forming a specified wire coil in the rotary electric machine byconnecting winding terminals of the cassette coils to each other.

According to the method for manufacturing the stator of the rotaryelectric machine having the above configuration, the cassette coil isattached to the stator core in such a manner that the innercircumferential side surface of each of the turns of the rectangularwire of the cassette coil is fitted to the step of the insulator. Inthis way, an elastic reaction force as that of a coil spring using therectangular wire can reliably be applied to the insulator.

In the method for manufacturing the stator of the rotary electricmachine according to the one aspect of the present disclosure, the shiftamount of the wire shape may be a magnitude of a twisting angle withrespect to the axis in the winding direction.

According to the method for manufacturing the stator of the rotaryelectric machine having the above configuration, a specified twistingangle with respect to the axis in the winding direction is applied tothe wire shape of at least one of the turns before attachment to thetooth or the insulator. In this way, an elastic reaction force that isgenerated by cancellation of the twisting angle of the wire can beapplied to the tooth or the insulator.

In the method for manufacturing the stator of the rotary electricmachine according to the one aspect of the present disclosure, the shiftamount of the wire shape may be a displacement amount along acircumferential direction of the stator core with respect to the axis inthe winding direction.

According to the method for manufacturing the stator of the rotaryelectric machine having the above configuration, a specifieddisplacement amount along the circumferential direction of the statorcore with respect to the axis in the winding direction is applied to thewire shape of at least one of the turns before the attachment to thetooth or the insulator. In this way, an elastic reaction force that isgenerated by cancellation of the displacement amount of the wire can beapplied to the tooth or the insulator.

A cassette coil for a rotary electric machine according to one aspect ofthe present disclosure includes rectangular wire. The rectangular wireis concentrically wound for the specified number of turns. Therectangular wire is wound by applying a shift amount with respect to anaxis in a winding direction to a wire shape of at least one of the turnsbefore being attached to a stator core of a stator of the rotaryelectric machine.

According to the cassette coil for the rotary electric machine havingthe above configuration, the cassette coil is formed by applying thespecified shift amount with respect to the axis in the winding directionto the wire shape of at least one of the turns before being attached tothe stator core. The cassette coil has the property of the coil springand can have the appropriate coil spring elasticity by using therectangular wire therefor. By using this coil spring elasticity, thecassette coil can be attached while applying the reaction force of thespring elasticity, which is generated by the cancellation of the shiftamount, to the stator core.

According to the aspects of the present disclosure, the cassette coilcan be fixed to the stator core without using the special fixing member.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments will be described below with reference to theaccompanying drawings, in which like numerals denote like elements, andwherein:

FIG. 1 is a top view of a stator of a rotary electric machine that ismanufactured by a method for manufacturing the stator of the rotaryelectric machine in an embodiment according to the present disclosure,in which the stator is seen from a lead side as an axial direction inwhich a power line is drawn;

FIG. 2 is a perspective view of a cassette coil that is wound around onetooth and that is seen from an inner side in a radial direction with thelead side in FIG. 1 being a lower side;

FIG. 3A is a view in which a stator yoke is removed from FIG. 2;

FIG. 3B is a perspective view of an insulator that is taken out fromFIG. 3A;

FIG. 3C is a perspective view of the cassette coil before being woundaround a stator core in FIG. 3A;

FIG. 3D is a perspective view of a state when the cassette coil in FIG.3C is attached to the stator core via the insulator in FIG. 3B;

FIG. 4 is a flowchart that shows each process of the method formanufacturing the stator of the rotary electric machine in theembodiment according to the present disclosure;

FIG. 5A is a view showing a method for winding a cassette coil of therelated art as a comparative example;

FIG. 5B is a view showing a method for winding the cassette coil for therotary electric machine in the embodiment according to the presentdisclosure;

FIG. 6 is a view showing another method for winding the cassette coilfor the rotary electric machine in the embodiment according to thepresent disclosure;

FIG. 7A is a view showing a reaction force that is generated when thecassette coil in FIG. 5B is attached to the stator core; and

FIG. 7B is a view showing a reaction force that is generated when thecassette coil in FIG. 6 is attached to the stator core.

DETAILED DESCRIPTION OF EMBODIMENTS

A detailed description will hereinafter be made on an embodimentaccording to the present disclosure by using the drawings. As a statorof a rotary electric machine that is manufactured by a method formanufacturing the stator of the rotary electric machine, a stator thatis used for a rotary electric machine mounted in a vehicle willhereinafter be described. However, it should be understood as anexemplification written for the purpose of explanation. Application ofthe stator of the rotary electric machine may not have be vehicleinstallation as long as a concentrically wound cassette coil is used.Shapes, dimensions, the number of teeth, the number of turns, materials,and the like, which will be described below, are merely illustrative forexplanation purposes and thus can appropriately be changed in accordancewith a specification of the stator of the rotary electric machine. Inthe following description, similar components are denoted by the samereference numeral in all of the drawings, and the description thereonwill not be repeated.

FIG. 1 is a view of a configuration of a rotary electric machine stator10 that is used for a rotary electric machine mounted in a vehicle, asthe stator of the rotary electric machine that is manufactured by themethod for manufacturing the stator of the rotary electric machine,which will be described below. Unless otherwise noted, the rotaryelectric machine stator 10 will hereinafter be referred to as a stator10. A power line 18 to be connected to a drive circuit, which is notshown, is drawn from the stator 10. The rotary electric machine, forwhich the stator 10 is used, is a motor generator that functions as amotor during power running of the vehicle and that also functions as agenerator during braking of the vehicle through control of the drivecircuit, and is a three-phase synchronous rotary electric machine. Therotary electric machine is configured by including: the stator 10 as astator shown in FIG. 1; and a rotor as an annular rotor that is disposedon a radially inner side of the stator 10 with a specified clearancebeing provided therebetween. The rotor is not shown in FIG. 1.

FIG. 1 is a top view of the stator 10 that is seen from a lead side inan axial direction. Of both sides of the stator 10 in the axialdirection, the lead side is a side on which the power line 18 is drawnfrom the stator 10. An opposite side from the lead side in the axialdirection is an anti-lead side. FIG. 1 shows a circumferentialdirection, the radial direction, and the axial direction of the stator10. Both side directions in the circumferential direction are aright-handed direction and a left-handed direction in the top view ofthe stator 10 that is seen from the lead side. Hereinafter, theright-handed direction will be referred to as a clockwise direction, andthe left-handed direction will be referred to as a counterclockwisedirection. Both side directions in the radial direction are aninner-side direction and an outer-side direction of a stator core 12.Both side directions in the axial direction are a lead side directionand an anti-lead side direction.

The stator 10 is configured by including the stator core 12, a cassettecoil 14 that is attached to the stator core 12, and an insulator 16 thatis arranged between the stator core 12 and the cassette coil 14.

The stator core 12 is an annular magnetic component and includes anannular stator yoke 20 and plural teeth 22 that are projected from thestator yoke 20 to the radially inner side. A space between the adjacentteeth 22 is a slot 24. The tooth 22 is a projected section to which thecassette coil 14 is attached and which thereby serves as a magneticpole.

Such a stator core 12 is formed by stacking plural pieces of annularthin magnetic sheets 28 (see FIG. 2), and each of the annular thinmagnetic sheets 28 is molded in a specified shape such that the statoryoke 20 and the tooth 22 are provided and that the slot 24 is formed.Both surfaces of the thin magnetic sheet 28 are subjected to electricalinsulation treatment. An electromagnetic steel sheet can be used as amaterial of the thin magnetic sheet 28. Instead of a stacked body of thethin magnetic sheets, an article that is formed by integrally moldingmagnetic powder in the specified shape may be used.

The cassette coil 14 is a concentrically wound coil and is formed bywinding one-phase wire around one of the teeth 22 for the specifiednumber of turns. The cassette coil 14 of a different phase is arrangedin the one slot 24 between the adjacent teeth 22.

Such a cassette coil 14 is a coil piece that is formed by winding leadwire with an insulation film for the specified number of turns by usinga specified coil former and removing the wound lead wire from the coilformer. The lead wire with the insulation film is not directly woundaround the tooth 22 of the stator 10 by using the slots 24 as the spaceson both sides of the tooth 22. Instead, the cassette coil 14 that is thecoil piece as a separate component from the stator core 12 is fitted andattached to the tooth 22. The cassette coil 14 is the coil piece that isformed with the lead wire on which insulation film is placed. Thiscassette coil 14 is a single coil formed by a method described below, inwhich a bobbin or the like is not used.

As element wire of the lead wire with the insulation film for thecassette coil 14, copper wire, copper-tin alloy wire, silver-platedcopper-tin alloy wire, or the like can be used. As the element wire,rectangular wire having a substantially rectangular cross-sectionalshape is used. As the insulation film, an enamel film of polyamide-imideis used. Instead of this, polyester-imide, polyimide, polyester, formal,or the like can be used.

One unit of the cassette coil 14 is attached to each of the teeth 22 ofthe stator core 12. In an example of FIG. 1, the stator core 12 has fiveU-phase teeth 22, five V-phase teeth 22, and five W-phase teeth 22, andone unit of the cassette coil 14 is attached to each one of thesefifteen teeth 22. In FIG. 1, the teeth 22, to which the cassette coils14 are respectively attached, are shown as U1 to U5 used for a U-phase,V1 to V5 used for a V-phase, and W1 to W5 used for a W-phase.

In the three-phase synchronous rotary electric machine, groups of theU-phase coil, the V-phase coil, and the W-phase coil, are sequentiallyarranged along the circumferential direction of the stator core 12. Forexample, the five U-phase cassette coils 14 are arranged along thecircumferential direction of the stator core 12 while separating fromeach other at intervals of three teeth. Similarly, the five V-phasecassette coils 14 are also arranged along the circumferential directionof the stator core 12 while separating from each other at intervals ofthree teeth, and the five W-phase cassette coils 14 are also arrangedalong the circumferential direction of the stator core 12 whileseparating from each other at intervals of three teeth.

Each of the cassette coils 14 has a winding start end and a windingfinish end of the wire. In the five cassette coils 14 of the same phasethat are arranged along the circumferential direction of the stator core12, the winding start end of the first cassette coil 14 is connected tothe power line 18. The winding finish end of the first cassette coil 14is connected to the winding start end of the second cassette coil 14,which separates therefrom at the interval of the three teeth, by jumperwire 26. The winding finish end of the second cassette coil 14 isconnected to the winding start end of the third cassette coil 14, whichseparates therefrom at the interval of the three teeth, by the jumperwire 26. This process is repeated, and the winding finish end of thelast fifth cassette coil 14 is connected to the winding finish end ofeach of the fifth cassette coils 14 of the other two phases and servesas a neutral point N. In FIG. 1, the jumper wire 26 for each of thephases is distinguished from each other and is shown as U-phase jumperwire 26U, V-phase jumper wire 26V, and W-phase jumper wire 26W.

For example, as to the U-phase wire coils, a U terminal of the threepower lines 18 is connected to the winding start end of the cassettecoil 14 of U1. The winding finish end thereof and the winding start endof the cassette coil 14 of U2 are connected by the jumper wire 26U. Thewinding finish end of the cassette coil 14 of U2 and the winding startend of the cassette coil 14 of U3 are connected by another jumper wire26U. This process is repeated, and the winding finish end of thecassette coil 14 of U5 serves as the neutral point N. The same appliesto the V-phase wire coils and the W-phase wire coils. Just as described,the winding start ends and the winding finish ends as winding terminalsof the cassette coils 14 are connected to each other by a specifiedconnection method, so as to form three-phase wire coils in the rotaryelectric machine. In this way, five U-phase magnetic poles thatcorrespond to U1 to U5, five V-phase magnetic poles that correspond toV1 to V5, and five W-phase magnetic poles that correspond to W1 to W5are formed.

The insulator 16 is an insulation body having a cylindrical shape thatis held between an inner circumferential side surface of the cassettecoil 14 and an outer circumferential side surface of the tooth 22 thatopposes the inner circumferential side surface of the cassette coil 14.The insulator 16 is fixed to the stator core 12 by fixing means such asadhesion. As such an insulator 16, an article that is formed by moldinga sheet having an electrical insulation property into a specified shapecan be used. As the sheet having the electrical insulation property, inaddition to paper, a plastic film can be used. Details of the insulator16 will be described below. Note that, in the case where electricalinsulation performance of the insulation film of the cassette coil 14 issufficient, and the like, the insulator 16 may not be used. Unlessotherwise noted, the insulator 16 will be used below.

The concentrically wound coil is wound in a specified annular shapewhile the lead wire is bent. Accordingly, depending on rigidity of thelead wire, like a coil spring, an elastic reaction force that urges thecoil to return to an original lead wire shape is exerted in thecircumferential direction and the radial direction. In this embodiment,the cassette coil 14 is fixed to the stator core 12 by actively usingthis elastic reaction force as the coil spring.

FIG. 2 is a view in which a magnetic pole 30 corresponding to U4 in FIG.1 is taken out, in which the axial direction is vertically reversed andthe lead side is shown as a lower side of the sheet to illustrate awinding method.

The tooth 22 is projected from the stator yoke 20 to the radially innerside, and a cross-sectional shape thereof that is parallel to a surfacealong the circumferential direction is a rectangular shape. The statoryoke 20 and the tooth 22 are formed by stacking the thin magnetic sheets28 in the same shape. Thus, height dimensions of the stator yoke 20 andthe tooth 22 along the axial direction are the same. Depending on aspecification of the stator 10, electromagnetic steel sheets ofdifferent types may be used for the stator yoke 20 and the tooth 22, soas to make the height dimensions thereof differ from each other.

The cassette coil 14 shown in FIG. 2 is being fitted to an outer sidesurface of the insulator 16. Thus, to distinguish the cassette coil 14from a cassette coil 60 (see FIG. 3C) as a pre-attachment coil piece,the cassette coil 14 may be referred to as a post-attachment cassettecoil 14. The rectangular wire in width W₀ and thickness t₀ is used forthe cassette coil 14, and the cassette coil 14 is being wound around anaxis in a winding direction for the specified number of turns with athickness direction as the radial direction. A wire shape of each of theturns of the rectangular wire is an annular rectangular shape in whichfour corners are rounded. The axis in the winding direction is an axisthat is parallel to the radial direction, and is an axis that passesthrough the center of the annular rectangular shape that is the wireshape of each of the turns. (The width W₀/the thickness t₀) of therectangular wire falls within a range over 1 to approximately 3.Depending on the specification of the stator 10, (the width W₀/thethickness t₀) of the rectangular wire may have a value(s) other than theabove.

A winding start end 32 of the post-attachment cassette coil 14 islocated near an intersection of a lead-side end of the tooth 22 and aradially outer-side end of the tooth 22. The rectangular wire is woundaround the axis in the winding direction from the winding start end 32in the counterclockwise direction with seven turns. The axis in thewinding direction is the axis that is parallel to the radial direction.A winding finish end 34 after the seven turns is located near anintersection of the lead-side end and a radially inner-side end of thetooth 22. Of four sides of the annular rectangular shape as the wireshape of each of the turns, two sides are parallel to the axialdirection, and the other two sides are parallel to the circumferentialdirection. Note that, along the radial direction, the radiallyinner-side end of the tooth 22 and a radially inner-side end of theinsulator 16 are further projected to the radially inner side from aradially inner-side end of the cassette coil 14.

FIG. 3A to FIG. 3D show relationships among the tooth 22, the insulator16, the post-attachment cassette coil 14 to the insulator 16, and thepre-attachment cassette coil 60 to the insulator 16.

FIG. 3A is a view of the magnetic pole 30 in which the stator yoke 20 inFIG. 2 is not shown, and corresponds to a view in which the insulator 16and the cassette coil 14 are assembled to the tooth 22. FIG. 3B is aperspective view of the insulator 16 that is obtained by exploding FIG.3A. FIG. 3C is a perspective view of the pre-attachment cassette coil60. FIG. 3D is a perspective view of the post-attachment cassette coil14 that is obtained by exploding FIG. 3A. In FIG. 3A to FIG. 3C, aposition corresponding to the insulator 16 is shown by connectingtwo-dot chain lines. In FIG. 3C and FIG. 3D, positions corresponding tothe winding start end 32 and the winding finish end 34 are shown byconnecting broken lines.

The insulator 16 shown in FIG. 3B has a back surface sheet section 40for electrically insulating the cassette coil 14 and the stator yoke 20from each other. Furthermore, the insulator 16 has a side wall sheetsection 42 that is connected to the back surface sheet section 40 andinsulates the inner circumferential side surface of the cassette coil 14and the outer circumferential side surface of the tooth 22 that opposesthe inner circumferential side surface of the cassette coil 14 from eachother. The back surface sheet section 40 has an opening through whichthe tooth 22 passes, and the side wall sheet section 42 is provided bybeing connected to an edge of the opening. The side wall sheet section42 is a cylindrical member that makes one turn along the outercircumferential side surface of the tooth 22.

The tooth 22 is a projected section whose cross-sectional shape that isperpendicular to the radial direction is the rectangular shape. Within arange of the rectangular cross-sectional shape where the cassette coil14 is attached, a side at a tip of the tooth 22 that is along thecircumferential direction is shorter than a side in a root section onthe stator yoke 20 side that is along the circumferential direction.That is, the tooth 22 has a tapered shape within the range where thecassette coil 14 is attached. In the radial direction, in a portion thatis projected to the radially inner side from the range where thecassette coil 14 is attached, length of the tooth 22 along thecircumferential direction is constant. Corresponding to this shape ofthe tooth 22, the side wall sheet section 42 of the insulator 16 has ashape that is tapered toward the tip side within a range where thecassette coil 14 is attached. In a portion that is projected to the tipside from the range where the cassette coil 14 is attached, length ofthe insulator 16 along the circumferential direction is constant.

The inner circumferential side surface of the rectangular wire of eachof the turns of the cassette coil 14 in an attached state comes incontact with an outer side surface of a side wall sheet 44 on theclockwise direction side and an outer side surface of a side wall sheet46 on the counterclockwise direction side in the circumferentialdirection in the side wall sheet section 42 of the insulator 16. Withinthe range where the cassette coil 14 is attached, the insulator 16 istapered toward the tip side. Accordingly, when the rectangular wire thathas the substantially rectangular cross-sectional shape is brought intocontact with the outer side surface of the tapered insulator 16, aclearance is formed between the inner circumferential side surface ofthe rectangular wire and the outer side surface of the insulator 16. Inorder to prevent generation of this clearance, a stair-shaped step 48whose shape follows the inner circumferential side surface of each ofthe turns of the rectangular wire is provided. In this way, when thecassette coil 14 is attached, the rectangular wire of each of the turnsof the cassette coil 14 is aligned and arranged along the steps 48 onthe outer side surfaces of the side wall sheets 44, 46 of the insulator16 without generating the unnecessary clearance.

In the side wall sheet section 42 of the insulator 16, a bulged section50 that is bulged to the lead side and a bulged section 52 that isbulged to the anti-lead side in the axial direction are provided tosecure a bending radius that is used when the rectangular wire is bentin the annular rectangular shape. The inner circumferential side surfaceof the rectangular wire of each of the turns of the cassette coil 14comes in contact with bulged outer side surfaces of the bulged sections50, 52.

In the pre-attachment cassette coil 60 shown in FIG. 3C, the rectangularwire is wound around the axis in the winding direction from the windingstart end 32 in the counterclockwise direction with seven turns, andthis is the same as the post-attachment cassette coil 14. (E-E) is anaxis in the winding direction and is an axis that is parallel to theradial direction and passes through the center of the wire shape of therectangular wire of each of the turns. The axis (E-E) in the windingdirection is also an axis that is parallel to the radial direction andpasses through the center of the cross-sectional shape of the tooth 22that is perpendicular to the radial direction. In the pre-attachmentcassette coil 60, when being wound with seven turns around the axis(E-E) in the winding direction, the wire shape of each of the turns istwisted around the axis (E-E) in the winding direction at a specifiedtwisting angle Δθ. The twisting angle Δθ is an angle at a time when thewire shape is twisted around the axis (E-E) in the winding direction ata small angle when the cassette coil 60 is seen as the coil spring. Thetwisting angle Δθ is an angle of a few degrees and thus differs from arotational angle that has an angle of 360 degrees per turn. The twistingangle Δθ is an angle at a time when the wire shape of each of the turnsis not changed and the entire wire shape is twisted around the axis(E-E) in the winding direction. The twisting angle Δθ in seven turns aredifferent one another.

As for the post-attachment cassette coil 14, the twisting angle Δθequals 0 degree. Accordingly, the twisting angle Δθ corresponds to anangular difference around the axis (E-E) in the winding directionbetween the wire shape of each of the turns in the post-attachmentcassette coil 14 and the wire shape of each of the turns in thepre-attachment cassette coil 60.

In view of the above, the twisting angle Δθ will be described bycomparing the pre-attachment cassette coil 60 and the post-attachmentcassette coil 14. FIG. 3D is a view, in which the cassette coil 14attached to the magnetic pole 30 is taken out. When being taken out ofthe magnetic pole 30, the cassette coil 14 returns to the state of thepre-attachment cassette coil 60 in FIG. 3C. Note that FIG. 3D shows thecassette coil 14 in the state of being attached to the magnetic pole 30.

In FIG. 3D, diagonal lines are added to a portion of a wire shape 36 ofthe rectangular wire in one turn that is on the innermost side in theradial direction of the seven turns. The wire shape 36 includes: a sidethat has the winding finish end 34 and is parallel to thecircumferential direction; and a side 38 that is before the said sideand is parallel to the axial direction. An angle between these two sidesis 90 degrees.

The two-dot chain lines in FIG. 3C indicate a portion corresponding tothe wire shape 36 in FIG. 3D, a portion including the side that has thewinding finish end 34 and is parallel to the circumferential direction,and the side 38 that is before the said side and is parallel to theaxial direction. A wire shape 62 of the rectangular wire in the one turnthat is on the innermost side in the radial direction of the seven turnsof the pre-attachment cassette coil 60 to the magnetic pole 30 includes:a side that has a winding finish end 64 and is parallel to thecircumferential direction; and a side 66 that is right before the saidside and is parallel to the axial direction.

Here, the twisting angle Δθ relates to the wire shape of the rectangularwire in the one turn that is on the innermost side in the radialdirection of the seven turns. In regard to the side that is parallel tothe axial direction, the twisting angle Δθ is an angular difference thatis generated when the side 38 of the post-attachment cassette coil 14and the side 66 of the pre-attachment cassette coil 60 overlap eachother. In regard to the side that is parallel to the circumferentialdirection, the twisting angle Δθ is an angular difference that isgenerated when the side that has the winding finish end 34 of thepost-attachment cassette coil 14 and the side that has the windingfinish end 64 of the pre-attachment cassette coil 60 overlap each other.Even when being applied with the twisting angle Δθ, the wire shape 62 isnot changed from the wire shape 36. The relationship “the wire shape62=the wire shape 36” remains the same, and the wire shape 62 is onlyrotated at the twisting angle Δθ, which is a slight angle within asurface along the circumferential direction.

The twisting angles Δθ in the seven turns of the rectangular wire aredifferent one another. If the seven turns of the rectangular wire aredistinguished one by one, the first turn that includes the winding startend 32 is set as (N=1) and the seventh turn that includes the windingfinish end 64 is set as (N=7), then the twisting angle Δθ of the (N=1)turn is the smallest and the twisting angle Δθ of the (N=7) turn is thelargest. In the example of FIG. 3C, a twisting angle Δθ (N=1) of thefirst turn is 0 degree, and a twisting angle Δθ (N=7) of the seventhturn is approximately 10 degrees. For the second turn to the sixth turn,the twisting angle is gradually increased within a range from 0 degreeto 10 degrees.

In a state where the specified twisting angle Δθ is applied to the wireshape of each of the turns of the rectangular wire, the pre-attachmentcassette coil 60 is wound around the axis (E-E) in the windingdirection, and is fixed and formed in such a shape. As a method forfixing the shape, an appropriate press molding method can be used. Thepre-attachment cassette coil 60 is attached to the tooth 22 via theinsulator 16 in FIG. 3B. At the time, each of the turns of therectangular wire is attached in such a manner as to follow the step 48of the insulator 16.

Because the cassette coil 60 has elasticity as the coil spring, thetwisting angle of the wire of each of the turns is canceled by theattachment. For example, in a case of the seventh turn, a wire portionhaving the wire shape 62, to which the twisting angle Δθ is applied, isattached to the tooth 22 via the insulator 16. Accordingly, the seventhturn elastically returns as the wire portion having the wire shape 36.The elastic reaction force at this time is applied to the step 48 of theinsulator 16. In this way, the cassette coil 14 is fixed to the statorcore 12 via the insulator 16 without using a special fixing member.

A detailed description will hereinafter be made on a method formanufacturing the stator 10 of the above configuration by using FIG. 4onward. FIG. 4 is a flowchart that shows each process of the method formanufacturing the stator 10. Here, the stator core 12 is formed (S10).The stator core 12 is formed by stacking the specified number of piecesof the annular thin magnetic sheets 28 that are molded in the specifiedshape. The electromagnetic steel sheet, both surfaces of which aresubjected to the electrical insulation treatment, is used as the thinmagnetic sheet 28.

Next, the insulator 16 with the step 48 described by using FIG. 3B isarranged in each of the teeth 22 of the stator core 12 (S12). S12 isperformed by fitting the insulator 16 from the tip side of each of theteeth 22.

Concurrently with S10 and S12 or prior to these, the pre-attachmentcassette coil 60 is formed (S14). In S14, the pre-attachment cassettecoil 60 is formed by using the rectangular wire as described by usingFIG. 3C and by winding each of the turns while the twisting angle Δθ ofthe wire of each of the turns with respect to the axis (E-E) in thewinding direction during winding around the tooth 22 is shifted fromeach other.

FIG. 5A and FIG. 5B are views of a method for forming a pre-attachmentcassette coil in comparison with the related art. In these views, thetooth has the same cross section along the radial direction.

FIG. 5A is a view of one example of a method for manufacturing aconcentrically wound cassette coil 15 in the related art. In the relatedart, a coil former 70 that has a predetermined cross-sectional shape isused for winding. The coil former 70 can rotate about a shaft 72 in thewinding direction. Here, the winding start end 32 of the rectangularwire is fixed at an appropriate position of the coil former 70 and isarranged along an outer circumference of the coil former 70. Then, thecoil former 70 rotates in a direction of an arrow in FIG. 5A about theshaft in the winding direction while feeding the rectangular wire alonga feeding direction 74 indicated by the arrow. Feeding in the feedingdirection 74 includes feeding in the radial direction and feeding in thecircumferential direction in accordance with the advancement of winding.In this way, the rectangular wire is wound in a spiral shape along theouter circumference of the coil former 70. A winding guide groove in thespiral shape may be provided in the coil former 70.

In the method for forming the pre-attachment cassette coil 60 describedby using FIG. 3C, a coil former for twisting formation that has thetwisting angle Δθ for each of the turns is prepared. Each of the turnsof the rectangular wire is wound in a similar method to that in FIG. 5Aby using the coil former for the twisting formation. In this way, thepre-attachment cassette coil 60 described by using FIG. 3C can beformed.

FIG. 5B is a view of another method for applying the twisting angle Δθto the wire shape of each of the turns. A cassette coil 61 in FIG. 5B isformed by performing an additional process on the cassette coil 15 thatis formed by the method shown in FIG. 5A. As the additional process, atwisting support shaft 76 is applied to one of round portions at cornersof the cassette coil 15, and the wire shape of each of the turns istwisted around the twisting support shaft 76 at the specified twistingangle Δθ. Here, “twisting” means that, as described by using FIG. 3C,the wire shape is rotated at the slight angle and is stopped at arotated position. In the example of FIG. 3C, the twisting angle Δθ ofthe seventh turn is approximately 10 degrees. As a method for fixing thetwisted shape, the appropriate press molding method can be used.

The above pre-attachment cassette coils 60, 61 are each formed byapplying the twisting angle Δθ to the wire shape of each of the turns.However, a method other than the above may be adopted. For example, thepre-attachment cassette coil may be formed by a method, in which aninitial distortion of a specified shift amount is applied to the wireshape of each of the turns with respect to the axis in the windingdirection. For a cassette coil 63 in FIG. 6, the cassette coil 15 thatis formed by the method shown in FIG. 5A is used, and, as the specifiedshift amount, a specified displacement amount ΔP in the circumferentialdirection is applied to the wire shape of each of the turns. Thedisplacement amount ΔP in turns are different one another. Thedisplacement amount ΔP of the first (N=1) turn counting from the windingstart end 32 is the smallest. The displacement amount ΔP is increased asN indicative of the number of the turn is increased, and thedisplacement amount ΔP of the seventh (N=7) turn is the largest. As amethod for fixing a shape, to which the displacement amount is applied,the appropriate press molding method can be used.

In the above description, the twisting angle Δθ is set as an angle inthe clockwise direction when seen from the inner sides of the cassettecoils 60, 61 in the radial direction; however, this may be set as anangle in the counterclockwise direction. In addition, the displacementamount ΔP of the cassette coil 63 is set as a displacement amount in theclockwise direction along the circumferential direction; however, thismay be set as a displacement amount in the counterclockwise directionalong the circumferential direction. Furthermore, the twisting angle Δθand the displacement amount ΔP may be combined. In the abovedescription, the twisting angle Δθ and the displacement amount ΔP inturns are different one another; however, the twisting angle Δθ and thedisplacement amount ΔP may differ in a portion of each of the turns fromthose in the rest of the portion of each of the turns. The twistingangle Δθ and the displacement amount ΔP are applied to the wire shape ofat least one of the turns. For example, the twisting angle Δθ or thedisplacement amount ΔP may be applied only to the seventh turn on theinnermost side in the radial direction. Note that the number of theturns is seven in the above description; however, the number of theturns may be other than seven.

Returning to FIG. 4, next, the cassette coil 60 that is formed in S14 isattached to the stator core 12 (S16). Here, the cassette coil 60 isattached to the insulator 16 that is arranged in the stator core 12 inS12. Instead of the cassette coil 60, the cassette coil 61 in FIG. 5B orthe cassette coil 63 in FIG. 6 may be used. In the cassette coil 60 thatremains the same as that formed in S12, the wire shape of each of theturns is applied with the specified shift amount and has the initialdistortion. The cassette coil 60 is attached as follows; the cassettecoil 60 is fitted from the tip sides of the tooth 22 and the insulator16, and the inner circumferential side surface of each of the turns ofthe rectangular wire is aligned and brought into surface contact withthe step 48 on the outer side surface of the insulator 16 whilecanceling shift of the wire shape of each of the turns.

FIG. 7A is a view of an action that is exerted when the cassette coil 60is attached to the outer side surface of the insulator 16 while thetwisting angle Δθ, which is the shift amount of the wire shape of eachof the turns, is canceled. In regard to the pre-attachment cassette coil60, twisting angle cancellation of (−Δθ) is performed thereon from astate of having the twisting angle Δθ. In this way, the cassette coil 60becomes the post-attachment cassette coil 14. The cassette coil 60 has aproperty as the coil spring. Thus, the cassette coil 60 is elasticallydeformed by the twisting angle cancellation of (−Δθ), and the elasticreaction force thereof is applied to the step 48 of the insulator 16.With the elastic reaction force, the cassette coil 14 is fixed to theinsulator 16 and is fixed to the stator core 12. The same applies to thecassette coil 61.

FIG. 7B is a view of an action that is exerted when the cassette coil 63is attached to the outer side surface of the insulator 16. In regard tothe pre-attachment cassette coil 63, displacement amount cancellation of(−ΔP) is performed thereon from a state of having the displacementamount ΔP. In this way, the cassette coil 63 becomes the post-attachmentcassette coil 14. The cassette coil 63 has a property as the coilspring. Thus, the cassette coil 63 is elastically deformed by thedisplacement amount cancellation of (−ΔP), and the elastic reactionforce thereof is applied to the step 48 of the insulator 16. With theelastic reaction force, the cassette coil 14 is fixed to the insulator16 and is fixed to the stator core 12.

The elastic reaction force is a force that attempts to cancel elasticdeformation caused by the cancellation of the specified shift amount. Inboth of the case of FIG. 7A and the case of FIG. 7B, a direction of thespecified shift amount is the counterclockwise direction with respect tothe circumferential direction. Accordingly, a direction of the elasticdeformation that cancels the shift amount is the clockwise directionwith respect to the circumferential direction. Thus, a direction of theelastic reaction force as a direction in which the elastic deformationis attempted to be canceled is the counterclockwise direction withrespect to the circumferential direction. This elastic reaction force inthe counterclockwise direction with respect to the circumferentialdirection is applied to the insulator 16 by the side of the wire shapeof the cassette coil 14 on the clockwise direction side with respect tothe circumferential direction among the two sides thereof that areparallel to the axial direction. FIG. 7A shows an elastic reaction force80, and FIG. 7B shows an elastic reaction force 82. With these elasticreaction forces 80, 82, the cassette coil 14 is fixed to the insulator16 and is fixed to the stator core 12.

Magnitudes of the elastic reaction forces 80, 82 that are required tofix the cassette coil 14 to the stator core 12 are defined in accordancewith specifications of the rotary electric machine, such as an operationenvironment. In order to generate the elastic reaction forces 80, 82 inthe defined magnitudes, the width W₀ and the thickness t₀ of therectangular wire as well as the rigidity of the material, the wireshape, the number of turns, the twisting angle Δθ, the displacementamount ΔP, and the like of the rectangular wire are set.

Returning to FIG. 4, the process in S16 is performed for each of theinsulators 16 that are respectively fitted to the teeth 22 of the statorcore 12. When the process in S16 is finished for all of the teeth 22, asindicated in FIG. 1, the winding terminals of the cassette coils 14 areconnected to each other by the specified connection method, and thespecified wire coils in the rotary electric machine are formed (S18).

In the above description, the insulator 16 is used. However, in the casewhere the electrical insulation performance of the cassette coil 14 issufficient and the insulator 16 need not be used, the process in S12 isskipped. In S16, the pre-attachment cassette coil 60 and the like aredirectly attached to an outer circumferential surface of the tooth 22.In this case, the elastic reaction force that is generated by thecancellation of the specified shift amount is directly applied from thecassette coil 14 to the tooth 22. In this way, the cassette coil 14 isfixed to the tooth 22 of the stator core 12.

Here, the embodiment will be summarized. The method for manufacturingthe stator of the rotary electric machine includes steps of: forming thestator core having plural teeth; forming the cassette coil by using andconcentrically winding the rectangular wire for the specified number ofturns, the cassette coil being formed by applying the specified shiftamount with respect to the axis in the winding direction to a wire shapeof at least one of the turns before being attached to the stator core;arranging an insulator on an outer circumferential side surface of thetooth, the insulator having a cylindrical shape that is held between aninner circumferential side surface of the cassette coil and the outercircumferential side surface of the tooth that opposes the innercircumferential side surface of the cassette coil and being providedwith a step on an outer side surface of the cylindrical shapecorresponding to an inner circumferential side surface of each of theturns of the rectangular wire; and bringing the inner circumferentialside surface of each of the turns of the rectangular wire into contactwith the step of the insulator while canceling the shift amount, andattaching the cassette coil.

What is claimed is:
 1. A cassette coil for a rotary electric machine, the rotary electric machine including a stator having a stator core, the cassette coil comprising: rectangular wire concentrically wound for the specified number of turns, the rectangular wire being wound by applying a specified shift amount with respect to an axis in a winding direction to a wire shape of at least one of the turns before being attached to the stator core. 